6th October 2015- A group of researchers in Germany recently published findings evidencing that runner's high is not just caused by exercise-induced endorphin release. A runner's high is a subjective sense of well-being some people experience after exercising for long periods of time. For decades, it was hypothesized that runner's high is caused by exercise-induced endorphin release. Long-distance runners have always described a runner's high as a sudden pleasant feeling of euphoria, anxiolysis, sedation, and analgesia. However, running increases blood levels of both endorphin (an opioid) and anadamide (an endocannabinoid).
The paper published by Fuss and colleagues shows that endocannabinoids may play a role. Using a combination of pharmacological, molecular genetics, and behavioral studies in mice, they discovered that wheel running increases endocannabinoids and reduces both anxiety and sensation of pain in mice. With the conclusion that for the first time, cannabinoid receptors are crucial for main aspects of a runner's high and not just exercise-induced endorphin release as perceived before. Sedation, in contrast, was not influenced by cannabinoid receptors and euphoria cannot be studied in mouse models.
Johannes Fuss et. al. A runner's high depends on cannabinoid receptors in mice. https://www.pnas.org/cgi/doi/10.1073/pnas.1514996112